Imaging detection apparatuses using X-ray imaging technologies are known to people. For example, in subways, airports and bus stations, personal bags and other items of passengers are detected by using the apparatuses, so as to check whether there are illegal transport articles such as radiation sources, explosives, drugs etc. At present, the threat of terrorist organization is serious, and thus the accuracy for identifying materials in the imaging detection apparatuses is very important.
In recent years, with the development of semiconductor technology, semiconductor detectors at room temperature have been used in many fields, such as nuclear physics, X-ray detection, gamma ray detection, astronomical detection, environmental monitoring, medical imaging etc. In particular, cadmium zinc telluride (CdZnTe, CZT for short) is considered to be the most promising radiation detection material due to its advantages such as excellent energy resolution, high detection efficiency and the ability to work at room temperature.
Compared with integral and indirect type radiation detectors, photon counting imaging using CZT semiconductor detectors has higher detection efficiency, a higher signal-to-noise ratio and a higher energy resolution. Therefore, it is possible to display images for a plurality of energy regions, and to identify materials by using information on the plurality of energy regions. Currently, imaging detection apparatuses for a plurality of energy regions have been proposed, and different divisions of energy regions can be applied to image display and material identification. In particular, the divisions of the energy regions may include equal energy region division, fine energy region division, optimized energy region division etc.
One way to implement a conventional system for detecting radiation of a plurality of energy regions is shown in FIG. 1. Specifically, in the system for detecting radiation of a plurality of energy regions shown in FIG. 1, a method of combining threshold devices and counters is employed. After rays as a detected object interact with the detector, electrons and holes are generated, Due to an electric field formed by the electrons and holes, signals are generated at anodes and cathodes of the detector, respectively. The signal is amplified, filtered and shaped to be transferred to a detection channel consisting of a plurality of threshold devices and a plurality of counters. Specifically, if amplitude of the signal is greater than a threshold set by the threshold device, a count value of the counter is added with 1. Therefore, the count value of the corresponding energy region can be obtained by setting different thresholds. In other words, by increasing a number of threshold devices and a number of counters, count values of more energy regions can be obtained. However, the drawback of this method is that the ASIC design is complex, and the combination of the threshold devices and the counters not only brings more power consumption, but also increases the noise of the system. Therefore, it cannot detect more energy regions in practice.
In order to achieve detection of more energy regions, a radiation detection system shown in FIG. 2 has been developed. This method can implement detection of multiple energy regions by adding an Analog Digital Converter (ADC) to each single channel or multiplexing one ADC among multiple channels. Specifically, in the system shown in FIG. 2, a detection signal is delivered to an ADC after being preprocessed, and then is processed by the ADC and transmitted to a FPGA to arrive at a computer, wherein the preprocessing may comprise performing processes on the detection signal, such as pre-amplification, filtering and shaping etc. By using the ADC, this method can detect more energy regions with its energy resolution being related to ADC accuracy. However, it should be noted that although FIG. 2 only shows a single channel of a conventional system for detecting radiation of a plurality of energy regions, the radiation detection system may include multiple channels. It should be also noted that although this method is simple, the implementation may occur many problems. In particular, in the radiation detection system, a plurality of ADCs are needed due to a large number of channels, and as a speed of the signal is high, requirements for the speed of the ADC is also relatively high, causing a high cost of the radiation detection system. In addition, in the circuit design, due to the addition of a plurality of ADCs, the FPGA needs more ports, which not only increases the overall power consumption of the system, but also makes the circuit design of the system more complex in practice and brings more uncertainty, and thereby the system has a poor practicability.
Therefore, there is a need to provide an apparatus for processing signals for a plurality of energy regions, and a system and method for detecting radiation of a plurality of energy regions, which can separate the analog circuit from the digital circuit, improve the energy resolution of the system, and simplify the design of the system.